classical

conforming to ancient Greek and Roman models in literature or art, or to later systems modeled upon them.

3.

marked by classicism:

classical simplicity.

4.

Music.

of, relating to, or constituting the formally and artistically more sophisticated and enduring types of music, as distinguished from popular and folk music and jazz. Classical music includes symphonies, operas, sonatas, song cycles, and lieder.

of, pertaining to, characterized by, or adhering to the well-ordered, chiefly homophonic musical style of the latter half of the 18th and the early 19th centuries:

Haydn and Mozart are classical composers.

5.

Architecture.

noting or pertaining to the architecture of ancient Greece and Rome, especially the religious and public architecture, characterized by the employment of orders.

noting or pertaining to any of several styles of architecture closely imitating the architecture of ancient Greece or Rome; neoclassic.

noting or pertaining to architectural details or motifs adapted from ancient Greek or Roman models.

(of an architectural design) simple, reposeful, well-proportioned, or symmetrical in a manner suggesting the architecture of ancient Greece and Rome.

6.

(often initial capital letter) pertaining to or designating the style of fine arts, especially painting and sculpture, developed in Greece during the 5th and 4th centuries b.c., chiefly characterized by balanced composition, the separation of figures from an architectural background, and the naturalistic rendering of anatomical details, spatial movement, and distribution of weight in a figure.

of or relating to a style of literature and art characterized by conformity to established treatments, taste, or critical standards, and by attention to form with the general effect of regularity, simplicity, balance, proportion, and controlled emotion (contrasted with romantic).

8.

pertaining to or versed in the ancient classics:

a classical scholar.

9.

relating to or teaching academic branches of knowledge, as the humanities, general sciences, etc., as distinguished from technical subjects.

10.

(of a given field of knowledge) accepted as standard and authoritative, as distinguished from novel or experimental:

classical

adj.

1590s, "of the highest rank" (originally in literature), from classic + -al (1). Classical music (1836) was defined originally against romantic music.

[I]n general, as now used, the term classical includes the composers active in instrumental music from somewhere about 1700 to say 1830. Hence the list includes among the great names those of Bach, his sons, Haydn, Mozart, Beethoven, Clementi, Dussek, Pleyel, Cramer, etc. The next step beyond the term classical is "modern romantic," the composers of which school may be taken to include all the writers for pianoforte from about 1829 (when Mendelssohn published the first "Songs without Words") down to the present. The term romantic in this sense means strongly marked, extraordinary, intending to tell stories and the like. ["Music, Its Ideals and Methods," W.S.B. Mathews, 1897]

But already by 1880s it was acknowledged the term had a double sense: Music that had withstood the test of time, as well as music of a style contrasted to "romantic." Later (early 20c.) it was contrasted to jazz (in this sense more often with reference to the orchestras than to the music itself). Still later in contrast to popular music generally (mid-20c.).